#include <iostream>
#include <cstdlib>
using namespace std;

int main()
{

	double miles {0.0};
	cout << "How many miles?\n";
	cin >> miles;

	if (!cin) {
		  cerr << "Sorry, that wasn't a number.\n";
		  return EXIT_FAILURE;
	
	}
	
	if (miles <= 0) || miles >= 100) {
		cerr << "Sorry, that wasn't a legitimate number.\n";
		return EXIT_FAILURE
	}

	//3 dollars, plus 70 cents for each 1/5 of a mile.
	// double dollars {3.00 + .70 * 5 * miles};
	
	double dollars {3.00 + 3.50 * miles};	//Simplier way to do the same thing.

	cout << dollars << " dollars\n";
	return EXIT_SUCCESS;

}